A conventional bar code system for recognition of products utilizes the principle of different optical reflection rates to input digital signals into a computer by optical scanning so as to recognize product information. For example, a product code is scanned and converted by computer software to a selling price being previously entered, such that the price of the product to be purchased is entered and recorded.
Referring to the bar code recognition system 40 shown in FIGS. 5A and 5B, a bar code 41 comprises black and white stripes of different widths and is affixed to a product 42 to represent a product code for the product 42. A bar code reader 43 is used to scan the bar code 41, wherein a CCD sensor or light-emitting element 45 of the bar code reader 43 emits light on the black and white stripes of the bar code 41 such that the white stripes reflect visible light of different wavelengths and the black stripes absorb visible light of different wavelengths. Then a lens 46 of the bar code reader 43 focuses the reflected light on a photoelectric converter 47 that converts the reflected light signals to corresponding digital electrical signals. The digital electrical signals are transmitted via an amplifier circuit 48 and a shaping circuit 49 back to a central processor of a computer, such that the product code can be recognized by the central processor and previously installed software of the computer. Therefore, a user can rapidly associate a product code on a product with product information such as selling price, discount condition, stock supply condition, borrowed and returned deadlines in case for a book, and so on, by simply scanning the product code and entering the related information via the computer software.
However, the above conventional recognition technique is inherent with a significant problem that the recognition accuracy thereof is only 95%, which is not good enough in practice. Moreover, since the bar code 41 utilizes stripes of different widths to achieve the differentiation effect, the design of the bar code 41 is restricted in terms of a limitation on the possible number of stripes being provided within a unit area. Further, the size of bar code may be increased according to different widths of the stripes used for the bar code, and such bar code is not suitable for recognition of small products.
In recent years, there has been developed a radio frequency identification (RFID) recognition technique using radio waves to transmit product recognition information, in place of the conventional bar code technique. Referring to FIG. 6, a RFID chip 50 that can emit radio waves is packaged on a tag 51, and then the tag 51 is affixed to a product to be recognized. Upon activation, the radio waves emitted by the chip 50 are transmitted to a reader 53 via an antenna 52 and then transmitted via information middleware 54 to a distant integration system 55 where recognition and processing of the wave signals are performed.
The RFID recognition technique has advantages such as data updating, large data storage capacity, high recognition accuracy, high data security, and so on, which can solve some of the problems caused by the conventional bar code technique. However, the RFID recognition technique still leads to significant drawbacks. Liquids or metals would often interfere with transmission of the radio waves to cause failure, such that the variety of products to which the RFID recognition technique is applicable becomes limited. For example, with respect to refrigerated fresh food sold in general supermarkets, condensed vapors or water may appear on packages thereof and impede the recognition function of the RFID chip. Furthermore, the RFID recognition system requiring a special antenna and a reader is relatively complex, and it is rather difficult to achieve packaging accuracy between the chip, the tag, and the antenna. This makes the RFID recognition system not cost-effective to fabricate and not suitable for mass production.
Therefore, the problem to be solved here is to provide an improved bar code and a recognition system and method thereof, which can eliminate the foregoing prior-art drawbacks when recognizing products.